Things went pretty shit between me and DH and and I walked out on him when DS was 4 months. Our relationship had descended into not a nice place, we argued all the time, we never spent time together, I was resentful of the fact he got to escape parenthood with work and socialising etc and things just became unbearable.
I was only away from home for about 5 days but it gave us both some time to look at what our relationship had turned in to and what we could do about it. Things didn't really start to return to normal between us though until DS was about a year old. We agreed to accept that we were going through a very tough time but that we had to just see it out and always remember that underneath the current difficulties we did love each other.
Having a baby can be very tough on even the best of relationships.
On a happier note though, we've just had our second baby and our relationship hasn't been negatively affected at all, if anything it's better because we knew what to expect this time in terms of what challenges will arise due to having a baby.
Every relationship reacts differently to the arrival of a baby but I imagine a lot of women will have periods where they hate their partner for some reason or another.
It may be a good idea to talk to each other beforehand about how you think your relationship may change etc and what support you think you will need from him etc, but as the saying goes "Nothing can prepare you for having a baby until you actually have one."
Congratulations on your pregnancy OP, and although your relationship may be absolutely fine always bear in mind that things will still be tough and rather than let any resentment build up try and talk to your DH honestly about how you are feeling of things start to annoy or upset you.